The present invention relates to printed wiring boards or cards and to methods of producing the same.
FIG. 13 illustrates a printed wiring board (or card) 1 having, on an edge thereof, tabs (or board edge contacts) 2 for establishing an electrical connection between board 1 and an external electronic apparatus. Board 1 is pluggable into and unpluggable from an edge connector of such an external apparatus. Tabs 2 are typically formed as a part of a copper circuit pattern and plated (e.g., with gold) to prevent an oxide film from being formed.
As shown in FIGS. 14 and 15, board 1 is produced from a panel 3 of a sufficient size to produce at least one printing wiring board 1 therefrom. On panel 3 are formed at least one predetermined circuit pattern layer and one insulating layer (not shown). A set of tabs 2 is formed as a part of the copper circuit pattern, and each tab includes an associated extension 4 which is to be used in the plating process (e.g., with gold). Tabs 2 are electroplated by passing an electric current through extensions 4. On the surface of the circuit pattern (except tabs 2 and extensions 4), a protective film (plating resist) is adhered so as not to electroplate the surface. Panel 3 is then cut along the double dotted lines shown in FIG. 15 using a known machine so as to produce board 1 of a desired shape. Since extensions 4 become unnecessary after the plating process, most portions of extensions 4 are cut away from each respective tab 2.
In this cutting process, an end portion 5 of the extension lines 4 at the cutting position may be peeled from the surface of the respective insulating layer of board 1, as shown in FIG. 16. In addition, swarf and burrs of the conductor may often be left on the end portion of the conductor. The peeling of such a conductor can result in eventual inoperability of the printed wiring board 1.
Since tabs 2 of board 1 are directly inserted into an edge-type connector of an external apparatus and come into contact with fingers of the edge-type connector, tabs 2 are susceptible to being peeled off. Particularly in the case of a build-up type printed wiring board, tabs 2 may be peeled off due to a low bonding strength between the conductors (tabs 2) and the insulating layer. In addition, the peeling of the conductor may damage the finger itself. For these reasons, it is strongly desired to prevent the peeling of the conductor.
In order to hopefully avoid such an occurrence, an edge of the printed wiring board (card) 1 may be beveled as shown by numeral 6 in FIG. 17. This beveling process is carried out to prevent the peeling of conductor 5 and to remove burrs. In addition, the beveling is also effective to reduce the plugging and unplugging forces of the board within its respective receiving connector. However, such a beveling process requires additional manufacturing steps (and costs) to produce such a product.
A primary object of the present invention is to provide a printed wiring board having a structure in which tabs are not easily peeled away from the board""s insulating layer.
Another object of the invention is to provide a method of producing such an advantageous product.
According to one aspect of the present invention, there is provided a printed wiring board comprising an insulating layer having a surface with a plurality of recesses therein, the recesses being formed along a predetermined edge portion of the insulating layer to extend through at least a portion of the insulating layer, a plurality of conductive tabs for establishing an electrical connection with an external electronic apparatus, selected ones of the tabs being formed on the surface of the insulating layer relative to a corresponding one of the recesses, and a plurality of conductive extensions located substantially on the surface of the insulating layer and being connected electrically to respective ones of the conductive tabs and extending into respective ones of the recesses.
According to another aspect of the invention, there is provided a method of making a printed wiring board comprising the steps of providing an insulating layer having a plurality of conductive tabs located thereon, forming a plurality of recesses within the insulating layer relative to the conductive tabs, forming conductive extensions which are connected electrically to the tabs and which extend within the recesses, and cutting the insulating layer along a predetermined line passing through the plurality of recesses.